refactor score to weightedNode structure

In many different scheduling strategies, a node is typically given
a certain weight based upon its values that are important to the
overall strategy. Exposing a weightedNode structure as well as a
new weightedNodeList type allows one to operate upon a set of nodes for
sorting purposes by assigning weights to each node and calling
sort.Sort() on a weightedNodeList.

Signed-off-by: Matthew Fisher <matthewf@opdemand.com>

scheduler/strategy/binpacking.go

@@ -19,7 +19,7 @@ func (p *BinPackingPlacementStrategy) Initialize() error {
 }
 
 func (p *BinPackingPlacementStrategy) PlaceContainer(config *dockerclient.ContainerConfig, nodes []cluster.Node) (cluster.Node, error) {
-	scores := scores{}
+	weightedNodes := weightedNodeList{}
 
 	for _, node := range nodes {
 		nodeMemory := node.TotalMemory()
@@ -43,39 +43,16 @@ func (p *BinPackingPlacementStrategy) PlaceContainer(config *dockerclient.Contai
 		}
 
 		if cpuScore <= 100 && memoryScore <= 100 {
-			scores = append(scores, &score{node: node, score: cpuScore + memoryScore})
+			weightedNodes = append(weightedNodes, &weightedNode{Node: node, Weight: cpuScore + memoryScore})
 		}
 	}
 
-	if len(scores) == 0 {
+	if len(weightedNodes) == 0 {
 		return nil, ErrNoResourcesAvailable
 	}
 
-	sort.Sort(scores)
+	// sort by highest weight
+	sort.Sort(sort.Reverse(weightedNodes))
 
-	return scores[0].node, nil
-}
-
-type score struct {
-	node  cluster.Node
-	score int64
-}
-
-type scores []*score
-
-func (s scores) Len() int {
-	return len(s)
-}
-
-func (s scores) Swap(i, j int) {
-	s[i], s[j] = s[j], s[i]
-}
-
-func (s scores) Less(i, j int) bool {
-	var (
-		ip = s[i]
-		jp = s[j]
-	)
-
-	return ip.score > jp.score
+	return weightedNodes[0].Node, nil
 }

scheduler/strategy/weighted_node.go

@@ -0,0 +1,30 @@
+package strategy
+
+import "github.com/docker/swarm/cluster"
+
+// WeightedNode represents a node in the cluster with a given weight, typically used for sorting
+// purposes.
+type weightedNode struct {
+	Node cluster.Node
+	// Weight is the inherent value of this node.
+	Weight int64
+}
+
+type weightedNodeList []*weightedNode
+
+func (n weightedNodeList) Len() int {
+	return len(n)
+}
+
+func (n weightedNodeList) Swap(i, j int) {
+	n[i], n[j] = n[j], n[i]
+}
+
+func (n weightedNodeList) Less(i, j int) bool {
+	var (
+		ip = n[i]
+		jp = n[j]
+	)
+
+	return ip.Weight < jp.Weight
+}